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Your search keyword '"Champion, Y."' showing total 146 results
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146 results on '"Champion, Y."'

1. Synthesis and characterization of core-shell structure silica-coated Fe29.5Ni70.5 nanoparticles

Author

Ammar, M, Mazaleyrat, F, Bonnet, J P, Audebert, P, Brosseau, A, Wang, G, and Champion, Y

Subjects
Condensed Matter - Materials Science
Abstract

In view of potential applications of magnetic particles in biomedicine and electromagnetic devices, we made use of the classical Stober method base-catalysed hydrolysis and condensation of tetraethoxysilane (TEOS) to encapsulate FeNi nanoparticles within a silica shell. An original stirring system under high power ultrasounds made possible to disperse the otherwise agglomerated particles. Sonication guaranteed particles to remain dispersed during the Stober synthesis and also improved the efficiency of the method. The coated particles are characterized by electron microscopy (TEM) and spectroscopy (EDX) showing a core-shell structure with a uniform layer of silica. Silica-coating does not affect the core magnetic properties. Indeed, all samples are ferromagnetic at 77 K and room temperature and the Curie point remains unchanged. Only the coercive force shows an unexpected non-monotonous dependence on silica layer thickness., Comment: Regular paper submited to international peer-reveiwed journal

Published
2007
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23. Development and Application of a Multifunctional Nanoindenter: Coupling to Electrical Measurements and Integration In-Situ in a Scanning Electron Microscope

Author

Comby-Dassonneville, S., primary, Charlot, F., additional, Martin, R., additional, Roussel-Dherbey, F., additional, Maniguet, L., additional, Pellerin, D., additional, Volpi, F., additional, Boujrouf, C., additional, Parry, G., additional, Braccini, M., additional, Iruela, S., additional, Antoni-Zdziobeka, A., additional, Champion, Y., additional, and Verdier, M., additional

Published
2019
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26. Nanostructured Cu-Cr alloy with high strength and electrical conductivity.

Author

Islamgaliev, R. K., Nesterov, K. M., Bourgon, J., Champion, Y., and Valiev, R. Z.

Subjects
NANOSTRUCTURED materials, ALLOYS, STRENGTH of materials, ELECTRIC conductivity, TRANSMISSION electron microscopy
Abstract

The influence of nanostructuring by high pressure torsion (HPT) on strength and electrical conductivity in the Cu-Cr alloy has been investigated. Microstructure of HPT samples was studied by transmission electron microscopy with special attention on precipitation of small chromium particles after various treatments. Effect of dynamic precipitation leading to enhancement of strength and electrical conductivity was observed. It is shown that nanostructuring leads to combination of high ultimate tensile strength of 790-840MPa, enhanced electrical conductivity of 81%-85% IACS and thermal stability up to 500 °C. The contributions of grain refinement and precipitation to enhanced properties of nanostructured alloy are discussed. [ABSTRACT FROM AUTHOR]

Published
2014
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29. Chemical heterogeneities in nanometric titanomagnetites prepared by soft chemistry and studied ex situ: evidence for Fe-segregation and oxidation kinetics

Author

Guigue-Millot, N, Champion, Y., Hytch, M.J., Bernard, F., Perriat, P., and Begin-Colin, S.

Subjects
Oxidation-reduction reaction -- Research, Iron compounds -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

The investigation of the heterogeneities in stoichiometric powders by a combination of averaging and local techniques, X-ray diffraction and Mossbauer spectrometry for an average analysis of powders, X-ray photoelectron spectroscopy for an analysis of the surface of the grains, are presented. Fe-segregation is found inside stoichimetric particles when the powders are studied.

Published
2001

30. Activation volume and deviation from Cottrell-Stokes law at small grain size

Author

Duhamel, C., Brechet, Y., Champion, Y., Science et Ingénierie des Matériaux et Procédés (SIMaP), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut National Polytechnique de Grenoble (INPG)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie et des Matériaux Paris-Est (ICMPE), and Institut de Chimie du CNRS (INC)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)

Subjects
sliding, STRAIN-RATE SENSITIVITY, Dislocations, Activation volume, Cottrell-Stokes law, Grain boundary, [CHIM.MATE]Chemical Sciences/Material chemistry, NANOCRYSTALLINE COPPER, Fine grained metal, TWINS, METALS, FLOW-STRESS, MICROSTRUCTURE, CU, BEHAVIOR
Abstract

International audience; Dependence of activation volume with flow stress is examined for metals with grain size lower than 0.31 mu m and larger than few tens of nanometers, where plastic deformation is most likely to be governed by a combination of grain boundary sliding and dislocations activity. The experimentally observed deviation from the classic linear behavior given by Cottrell-Stokes law [Basinski, Z.S., 1974. Forest hardening in face centered cubic metals. Scripts Metallurgica 8, 1301-1308] is analyzed, thanks to a modified Orowan equation taking into account of the grain boundaries sliding coupled to dislocations activity. These results are compared to experimental measurements of the activation volume, between room temperature and 120 degrees C, for a copper nanostructure with a grain size of 100 nm. A constant activation volume is observed at low stress (or high temperature) followed by an increase of activation volume with stress (inverse Cottrell-Stokes behavior). This analysis follows our initial experiments on this fine grained metal prepared by powder metallurgy, which exhibits ductility at near constant stress and strain rate

Published
2010

44. Gas Phase Synthesis of Nanopowders.

Author

Bréchignac, Catherine, Houdy, Philippe, Lahmani, Marcel, and Champion, Y.

Abstract

The aim of gas phase synthesis is to achieve the condensation of nanopowders with maximal specific surface area (see below for the definition), or in other words, to obtain nanoparticles that are not connected by strong chemical bonds (intergrain regions called grain boundaries; see, for example, the discussion of mechanical grinding in Chap. 19). When the contact region is partial, it is called a neck or bridge, a term taken from the field of sintering (see Chap. 21). [ABSTRACT FROM AUTHOR]

Published
2008
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